The present invention generally relates to facsimile machines and recording control methods therefor, and more particularly to a facsimile machine which is provided with a communication means for communicating in both Group-III (G3) and Group-IV (G4) modes, and a recording control method for preventing deterioration of the image received in the G3 and G4 modes of such a facsimile machine.
According to the CCITT standards, the resolution in the main scanning direction is set to 8 lines/mm and the resolution in the sub scanning direction is set to 7.7 lines/mm or 3.85 lines/mm for the G3 mode. On the other hand, the resolution is set to 200 dots/inch (dpi) or 400 dpi for the G4 mode. The resolution of 8 lines/mm corresponds to 0.125 mm/dot, and the resolution of 7.7 lines/mm corresponds to 0.130 mm/dot. The resolution of 200 dpi corresponds to 0.127 mm/dot.
In other words, in the millimeter system, the dot width in the main scanning direction is narrower and the dot width in the sub scanning direction is wider compared to those of the inch system. Hence, the amount of information transmitted and received in the millimeter system is larger than that of the inch system for the main scanning direction and is smaller than that of the inch system for the sub scanning direction. For this reason, the line density must be switched for the case where the communication is made in the G3 mode and for the case where the communication is made in the G4 mode.
In a conventional facsimile machine which is provided with a communication means for communicating in both G3 and G4 modes, the system of a scanner and a plotter thereof is fixed and made to conform to either the millimeter system or the inch system. Accordingly, if a receiving facsimile machine having an inch system plotter receives image information from a transmitting facsimile machine having a millimeter system scanner in the G3 mode, for example, the recorded image output from the receiving facsimile machine is expanded in the main scanning direction and is reduced in the sub scanning direction compared to the original image transmitted from the transmitting facsimile machine. In order to eliminate this problem, pixels in the main scanning direction are decimated (or thinned out) and the lines in the sub scanning direction are added so as to match the magnifications of the original image and the recorded image.
However, if the number of pixels and lines are decreased or increased at the receiving facsimile machine depending on the scanner of the transmitting facsimile machine and the plotter of the receiving facsimile machine, there is a problem in that a complex signal processing must be carried out in the receiving facsimile machine. In addition, there are problems in that the original image cannot be reproduced with a fine fidelity and that the image quality of the recorded image becomes poor.